A hypertrophic scar is an excessive wound scar which by definition has grown in size beyond that required for normal wound healing. Hypertrophic scars can emerge from many wound types, such as from a burn or a sharp incision. Keloids, a more severe form of hypertrophic wound scars, form firm dermal nodules of scar which are most commonly preceded by trauma at the site of origin. They are usually larger than hypertrophic scars and differ in that they frequently invade the normal skin adjacent to the wound.
Hypertrophic scars and keloids result from an over-production of cells, collagen and proteoglycan [Linares, H. A. and Larson, D. L., Plast. Reconst. Surg., 62:589 (1978); Linares, H. A., Plast. Reconstr. Surg., 818-820 (1983)]. Histologically, these lesions are characterized by randomly distributed tissue bundles consisting of uniaxially oriented extracellular matrix and cells. In these scars, the overproduction and compaction of collagen and proteoglycans [Shetlar, M. R. et al., Burns 4:14 (1977)] exceeds the proliferation of cells. These histological observations suggest that the lesions result from loss of the normal control mechanisms which regulate the synthesis of extracellular matrix during would healing [Shetlar. M. R. et al., Burns 4:14 (1977)].
Existing therapy for hypertrophic scars and keloids, includes surgery, mechanical pressure, steroids, x-ray irradiation and cryotherapy. There are many disadvantages associated with each of these methods. Surgical removal of the scar tissue is often incomplete and can result in the development of hypertrophic scars and keloids at the incision and suture points. Steroid treatments are unpredictable and often result in depigmentation of the skin. X-ray therapy is the only predictably effective treatment to date; however, because of its potential for causing cancer, it is not generally recommended or accepted.
Compositions comprising tripeptides, tetrapeptides and pentapeptides have been shown to inhibit biosynthesis of collagen and may be used to treat diseases caused by excess accumulation of collagen (Mitsubishi Chem., Japanese Patent Nos. 52083545, Jul. 12, 1977, and 52025768, Feb. 25, 1977).
Recently, the effects of applying silastic sheets onto the surface of hypertrophic scars was studied and shown to shrink and soften scar tissue. [Ohmori, S. Aesthetic Plastic Surgery 12:95-99 (1988)].
Despite the various treatments presently available, there is no widely accepted and predictably effective means for preventing or treating hypertrophic scars or keloids.